The present invention generally relates to sensing technology that employs electromechanical sensing devices, such as micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS). More particularly, this invention relates to sensing systems and methods capable of monitoring environmental parameters to which a body may be subjected, particular but nonlimiting examples of which are pressure and acceleration resulting from blasts and impacts sustained by a body, including a living body.
Wireless sensor systems are known that have the capability for high reliability, efficiency, and performance. Such systems can be employed in a wide range of applications including supply-chain and logistics, industrial and structural monitoring, healthcare, homeland security, and defense. Generally, it is desired to minimize the power dissipation, size, and cost of these systems by making them low-power and/or operate without a battery. Furthermore, in many applications a batteryless operation is needed due to lack of battery replacement feasibility, or to meet stringent cost, form factor, and lifetime requirements. One approach to addressing this need is scavenging energy from environmental sources such as ambient heat, radio and magnetic waves, vibrations, and light. However, in many situations, these environmental energy sources are not adequately available to power a sensor. Another approach is to remotely power wireless sensor systems by inductive or electromagnetic coupling, storing energy on a suitable energy storage device, such as one or more integrated capacitors or miniature batteries, and performing sensor operations over short periods of time to minimize the discharge rate of the energy storage device. These approaches typically benefit from miniaturization of the sensing element or elements. For example, micro-electromechanical system (MEMS) and nano-electromechanical system (NEMS) sensors have been developed that can be placed in or on an object or a living body for continuous monitoring. Various types of electromechanical sensors have been developed for sensing a wide variety of parameters, including but are not limited to temperature, pressure, acceleration (including impact or shock), vibration, impact, motion, and chemical content.
There are many health issues that would benefit from a real-time monitoring capability, including the severity of an environmental condition encountered by an individual. For example, medical treatment of athletes and military personnel subjected to sudden decelerations (such as impacts or shocks) and military personnel subjected to bomb blasts would be facilitated if medical personnel had a more immediate and clearer understanding of the severity of the impact or blast to which the person was subjected, and therefore the likelihood that the individual has suffered from head trauma and the likely severity of that trauma.
For treatment of blast victims, current injury models look at one type of exposure data to estimate the severity of a blast to which the victim was exposed. However, these models require more epidemiological studies on actual blast victims to determine optimal parameters for monitoring. Because the brain is a very complex system, there is no current consensus of optimal monitoring parameters for determining the many different types of brain injury. One parameter that is currently monitored is head acceleration, which can aid in the diagnosis of brain injuries. Current monitoring systems place accelerometers on the helmets of soldiers to record blast data. However, the data from these sensors are not quickly and readily available to a field medic or other medical personnel, and do not correlate well with the actual acceleration of the head. Furthermore, a technical complication of these systems is that the transfer function from motion of the helmet to motion of the head is different for every individual, and can depend on the fit of the helmet, tightness of the chin strap, how the helmet is worn, and many other factors that vary from individual to individual.
Another approach to diagnosing and treating blast victims is to assess brain injury due to the shock wave pulse. Though research involving animal studies have been conducted, a difficulty encountered when monitoring blast pressure waves is that most pressure sensors are directional, and it is therefore difficult to measure the shock wave pulse from a blast of unknown direction. In addition, it is difficult to reconstruct data and then apply the data to a traumatic injury after the fact due to human reactions to the event that can affect the data (reflexes). Consequently, the use of the shock wave pulse to diagnose and treat blast victims has been primarily limited to laboratory tests.
To be practical and widely accepted for applications of the type discussed above, suitable sensing devices would preferably be small and unobtrusive, have a long life, and be disposable, necessitating that their cost must be very low, yet also capable of accurately monitoring many types of trauma on a wide range of individuals performing a wide variety of activities. However, existing impact sensing systems are typically large, heavy and very expensive, consume a significant amount of power, and require batteries that must be changed on a fairly regular basis. Aside from players of high impact sports, it is nearly impossible to predict the occurrence of head impact and the subsequent trauma. Consequently, currently available systems are not widely used, and then typically limited to occasional uses, such as monitoring deceleration or impact on equipment worn by athletes, such as helmets of the types worn in hockey or American football. Still, and for reasons stated previously, such uses often provide data that do not correlate well with the actual deceleration of the head.